Quick return drive linkage



Aug. 20, 1968 H. s. MCGOWAN 3,397,585

QUICK RETURN DRIVE LINKAGE Filed Jan. 5, 1966 I /4 i, //3 9 /a /2 9 DRIVE |o=| MECHANISM GENEVA O 'NPUT INVENTOR. HAROLD S. M GOWAN ATTORNEY United States Patent 3,397,585 QUICK RETURN DRIVE LINKAGE Harold S. McGowan, Cedar Rapids, Iowa, assignor to Collins Radio Company, Cedar Rapids, Iowa, a corporation of Iowa Filed Jan. 3, 1966, Ser. No. 518,364 Claims. (Cl. 74-75) ABSTRACT OF THE DISCLOSURE The structure comprises a transfer mechanism in a counter for intermittently transferring motion from a first transfer wheel to a second counter wheel wherein the second counter wheel moves over a smaller arc than the first wheel to indicate a fewer number of digits and in which the operation is reversible.

This invention relates in general to counter mechanisms and in particular to a linkage mechanism in a counter which allows a limited number of numerals to be presented on one of the counter wheels.

Conventional Geneva movements and counters are well known, however, normally they consist of indicator drums carrying numerals from 0 through 9 with ten to one Geneva movements between adjacent counter drums so as to indicate units, tens, hundreds, etc. Occasionally applications arise wherein only some of the numerals from 0 through 9 are to be indicated. For example, in distance measuring equipment used in aircraft navigation, the maximum range of radio reception might be 300 miles. Thus, a counter might be required which indicates any distance from 0 to 299 miles. Only the units and tens counter drums would indicate all numerals from 0 through 9 but the hundreds counter drum would need to indicate only 0, 1 and 2.

The present invention provides a counter mechanism which allows bidirectional drive of an input shaft to a counter which is capable of indicating all the numerals on certain of the counter drums but which limits one of the counter drums position to less than ten positions.

It is an object of the present invention to provide a bidirectional counter which utilizes conventional Geneva movement transfer mechanisms between certain of the counter drums but has a new and novel drive mechanism between other drums.

A feature of this invention is found in the provision for a crank arm and linkage which replaces a conventional Geneva transfer between counter drums of an indicator.

Further objects, features, and advantages of this invention will become apparent from the following description and claims when read in view of the accompanying drawings, in which:

FIGURE 1 is a schematic illustration of the counter according to this invention;

FIGURE 2 is an illustration of the drive mechanism illustrated in FIGURE 1;

FIGURE 3 is a perspective view of the transfer gears of the drive mechanism; and,

FIGURE 4 illustrates a modification of the invention wherein the drive mechanism allows indication of only two numerals.

FIGURE 1 discloses an input shaft which carries a counter drum 11. The input shaft 10 is connected to a suitable function to be monitored such that one-tenth revolution of shaft 10 indicates a One unit increment. Thus, the counter drum 11 indicates any units between 0 and 9. The shaft 10 is connected to a ten to one Geneva mechanism 12 of conventional type such that its output shaft 13 rotates 36 degrees, or one-tenth of a revolution each time the shaft 10 makes a complete revolution. A

3,397,585 Patented Aug. 20, 1968 "ice counter drum 14 carrying numerals from 0 through 9 is carried on shaft 13 and indicates tens, Thus, counter drums 14 and 11, respectively, show the tens and units being counted.

A third counter drum 16 which indicates the hundreds is carried on oscillatory shaft 17. In a particular application, it is desired that the hundreds drum 16 only indicate one of three positions and in a particular example, 0, 1 and 2 are to be indicated. Thus, the counter of FIGURE 1 is capable of indicating any number between 0, .at which time all three counters would indicate 0, and 299, at which time counter drum 16 would be in the 2 position and counter drums 14 and 11 would be in the 9 positions. Since in some applications the maximum indication is limited, the remaining numbers need not occur on the counter drum 16.

The novel feature of this invention is found in the drive mechanism 18 between the shaft 13 which carries counter drum 14 and shaft 17 which carries the counter drum 16. The novel drive mechanism is illustrated in FIGURES 2 and 3. Shaft 13 carries a two-toothed gear 19 which has a pair of teeth 21 and 22 on a smaller radius portion 23 and a notch 24 formed on a larger radius portion 26. The notch 24 shows up better in FIGURE 3 which is a perspective view of the two-toothed gear 19. The twotoothed gear engages a transfer gear 27 formed with 12 teeth. Four of the teeth, 28, 29, 31 and 32, extend across both portions of the two-toothed gear 19 and the intermediate gear teeth 33 of gear 27 are in alignment with the portion 23 only.

The large radius portion 26 of the two-toothed gear 19 engages the long teeth 28, 29, 31 and 32 to lock the gear in a fixed position until a transfer occurs. For each revolution of the two toothed gear 19, a transfer occurs and rotates shaft 34 which supports the transfer gear 27 ninety degrees or one-quarter of a revolution. A gear 36 is also carried on shaft 34 and is in mesh with another gear 37 supported on a shaft 35. The gears 36 and 37 have a gear ratio such that gear 37 rotates degrees each time gear 36 rotates ninety degrees.

The hundreds counter shaft 17 has a crank arm 38 nonrotatably attached to it by means of a clamp screw 39. A link 41 extends from a pivot pin 42 on crank arm 38 to a pin 43 attached to gear 37.

The length of the linkage 41 and crank arm 38 and placement of pins 42 and 43 is such that the oscillatory shaft 17 is rotated 36 degrees when the gear 37 changes position by 120 degrees on two occasions and 72 degrees when the gear 37 changes 120 degrees the third occasion. Stated differently, in the position shown in FIGURE 2, the shaft 17 is at the 1 position. When gear 37 rotates counterclockwise 120 degrees, the linkage 41 will move the shaft 17 to the 0 position which is 36 degrees counterclockwise from the 1 position. When the gear 37 rotates another 120 degrees counterclockwise, the linkage 41 will move shaft 17 clockwise 72 degrees from the 0 to the 2 position. When a third 120 degree counterclockwise rotation of gear 37 occurs, linkage 41 will move shaft 17, 36 degrees counterclockwise from the 2 to the l position. In other words, the counter drum 16 is allowed to only indicate 0, 1 or 2.

The counter maybe driven bidirectionally such that gear 37 moves either clockwise or counterclockwise or the direction of rotation may be changed at any time and counter drum 16 will only. indicate 0, 1 or 2.

FIGURE 4 illustrates a modification wherein it is desired to move shaft 17 such that only two positions are indicated by shaft 17. This is accomplished by choosing a gear 44 which mates with gear 36 that rotates degrees each time a transfer occurs between the two-toothed gear 19 and transfer gear 27. A linkage 46 has one end attached to pivot pin 42 on crank arm 38. The other end of linkage 46 is attached to pivot pin 47 mounted on gear 44. Each time gear 44 rotates 180 degrees, the shaft 17 moves 36 degrees between and 1.

It is to be realized that the crank arm 38, the links 41 and 46 and size of gears 37 and 44 and the position of pins 42, 43 and 47 must be such that counter drum 16 rotates the desired amount. Thus, these lengths and positions are not arbitrary but must be carefully chosen.

It is seen that this invention provides a counter mechanism which allows a limited range of indication on one counter drum and although it has been described with respect to particular embodiments thereof, it is not to be so limited, as changes and modifications may be made therein which are within the spirit and scope of the invention as defined by the appended claims.

I claim:

1. A drive mechanism for a counter mechanism having input and output shafts comprising an intermediate shaft, means connected between the input shaft and intermediate shaft to intermittently rotate the intermediate shaft each time the input shaft makes a revolution, a first crank arm connected to the output shaft, a second crank arm connected to the intermediate shaft, a link joining the first and second crank arms, said means connected between the input shaft and intermediate shaft comprising a twotoothed gear carried on the input shaft, an idler shaft rotatably supported adjacent the two-toothed gear, a transfer gear carried on the idler shaft and in mesh with the two-toothed gear, a drive gear carried on the idler shaft, and a driven gear in mesh with the drive gear carried on the intermediate shaft.

2. In apparatus according to claim 1 wherein the driven gear rotates degrees each time the input shaft makes afull rotation.

3. In apparatus according to claim 1 wherein the driven gear rotates degrees each time the input shaft rotates 360 degrees.

4. In apparatus according to claim 2 wherein the output shaft moves 36 degrees in a first direction during two successive unidirectional 120 degree changes of the driven gear and moves 72 degrees in a reverse direction during a third successive unidirectional 120 degree change of the driven gear.

5. In apparatus according to claim 3 wherein the output shaft moves 36 degrees in a first direction for a first 180 change in position of the driven gear and moves 36 in the reverse direction for a subsequent 180 unidirectional change in the position of the driven gear;

References Cited UNITED STATES PATENTS 7 48,927 7/1865 Giroud 74436 469,003 2/1892 Weiss 74436 X 489,703 1/1893 Balzer 74-436 X 1,751,446 3/1930 Cammack 74-436 X 2,478,679 8/1949 Bartelson 74-436 X 2,589,940 3/1952 Hayek 744 36 FOREIGN PATENTS 888,445 9/ 1943 France.

W. S. RATLIFF, Assistant Examiner.

FRED C. MATTERN, 1a., Primal Examiner. 

